#155 : Embryo Thaw and Biopsy - A Clinical Guide for Patients

Abstract

Background and Aims: Preimplantation genetic testing allows the selection of chromosomally normal embryos for transfer, and therefore may reduce the time required to live birth. Some patients request to perform biopsy on previously cryopreserved embryos. This includes situations where the embryos were frozen untested, or no result was obtained from the initial trophectoderm biopsy. Method: We analysed the outcomes of 108 embryos over 3 years in the effort to provide guidance to patients in terms of the expectations when considering performing thaw and biopsy on cryopreserved embryos. This includes 32 untested embryos (planned for PGT) (Group A), 45 embryos frozen without the intention of testing (Group B) and 34 embryos that had no results obtained in the first biopsy (Group C). The developmental timing of the embryos in the initial culture and the extended culture timing following thawing, was examined using timelapse footage. Results: Among the 108 embryos that were thawed and subsequently cultured, 78.7% embryos were suitable for biopsy with an average of 8.5 h in extended culture. Group A had the lowest proportion of embryos suitable to biopsy after extended culture (56.3%), which is significantly lower than Group B (83.3%, P=0.0181) and Group C (94.1%, P=0.0004). Interestingly, Group A had the lowest proportion of euploid embryos (16.7%), followed by Group B (40.0%) and Group C (46.9%). Interestingly, of the Group C embryos that previously failed to amplify only 26.7% were euploid, compared to 64.7% for those that previously amplified but failed to pass quality control. There was no correlation between time to blastulate, time to form full blastocyst or culture time and euploidy rate. At the time of our study, 18 of the 32 euploid embryos were thawed and transferred, resulting in 44.4% clinical pregnancy rate. Conclusion: This analysis provides important information to guide patients’ expectations at a clinical level.